This application claims the priority of German patent document 199 57 151.1, filed Nov. 27 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a gearshift device for a motor vehicle.
In modern motor vehicles, the demands on gearshift devices are steadily increasing with respect not only to comfort, but also reliability, constructional space and weight, and with regard to supporting a driver of a motor vehicle. An advantageous effect can frequently be achieved by replacing mechanical components or assemblies by electronic components and assemblies.
As a rule, a gearshift device has an input unit for receiving input data or, a driver""s request. In most cases, the input unit is constructed as a gearshift lever which is connected to a gearbox via a rod linkage.
U.S. Pat. No. 4,790,204, discloses a generic gearshift in which a mechanical connection between an input unit and an automatic gearbox is replaced by an electronic assembly, making it possible to reduce components, weight, constructional space and assembly effort. The input unit has an input device with pushbuttons for selecting from amongst various gearshift positions, such as, for example, a park position P, a neutral position N, a drive position D, etc. The input device is electrically connected via a controller to an actuating unit which is mounted on an outer side of a gearbox housing and acts on an actuating lever. When an accelerator pedal is completely pushed down, a second controller receives a signal and drives a kick-down lever on the gearbox by means of the actuating unit.
One object of the present invention is to provide a gearshift device of the generic type which achieves enhanced reliability and comfort.
This and other objects and advantages are achieved by the gearshift device according to the invention, in which an input unit for receiving input data is connected via at least one data line to a first controller for controlling an actuator unit for adjusting a gearbox (such as an automatic gearbox of a motor vehicle). At least one second controller is also provided, which is independent of the first controller, and is also connected to the input unit via at least one data line. In the case of a fault in the first controller, the actuator unit can be controlled by the second controller at least partially correspondingly to the first controller. Due to the second controller, a high reliability can be achieved without any additional mechanical assembly. Advantageously, the second controller is also used for monitoring the first controller; it receives at least in part (and preferably completely) the same input data as the first controller and performs at least partly (and preferably entirely) the same evaluation and comparing the output variables for the purpose of monitoring. This saves an additional monitoring unit.
In the case of a fault, and an unacceptable deviation of the output variables, the second controller deactivates the first controller and at least partially takes over the operation of the first controller, making it possible to avoid having an additional unit for disconnecting the first controller. In this arrangement, the controllers are advantageously connected to the actuator unit via tristate lines, which supply information and electrical power for the actuator unit. Having a direct data line between the controllers can be avoided. Furthermore, the tristate lines can be advantageously used for deactivating the first controller by means of the second controller, in that the tristate lines of the controllers are connected to one another; in the case of a fault, the second controller short-circuits at least one tristate line, thereby deactivating the first controller via a current limiter. A current limiter which, as a rule, already exists, can be additionally used for disconnecting the first controller, wherein the current limiter can be integrated in the controller or also constructed as a separate unit.
If a fault occurs while the controller (or the first controller) is in a deactivated state, the activator unit assumes or maintains a position in which a flow of force between the gearbox and an internal combustion engine is interrupted. Accordingly, it is always possible to achieve a safe state for the gearbox and, especially, for the motor vehicle and its passengers. This can be achieved by means of various known actuators; for example by means of a hydraulic actuator which, in the deactivated state, moves into an initial position by means of a spring force or, advantageously, by means of an electromagnetic actuator comprising a spring mechanism which, in the deactivated state, holds an armature in a neutral position between two pole faces of electromagnets. Starting with a safe state, the second controller can subsequently take over the control of the actuator unit.
The controllers are advantageously connected to a data network of the motor vehicle, as a result of which vehicle data such as speed, speed sense, temperature, etc. can be taken into consideration in controlling the actuator unit. It is possible to use existing sensors and avoid using additional sensors at least to a large extent. It is also possible to transmit information from the controllers to other controllers via the data network, for example the power of the internal combustion engine can be advantageously reduced in a deactivated state of the actuator unit in order to avoid unwanted high idling revolutions.
Apart from the control functions of the gearbox, one or both controllers can be used for other operations, for example for an engine control, etc., as a result of which additional components and constructional space can be saved.
In one embodiment of the invention, the actuator unit has at least one first actuator and one second actuator, which is independent of the first actuator. The first actuator is used, in normal operation, for setting a drive position and a neutral position at the gearbox, and the second actuator is used for operating a parking lock in a park position of the gearbox. In an automatic gearbox, a selector slide can be advantageously constructed with only three positions instead of four positions, which makes it possible to save costs and constructional space. Furthermore, additional degrees of freedom are obtained in the driving and in the arrangement of the actuators. The actuators can be advantageously driven independently of one another in various situations; for example a drive position D or R can be set at the gearbox by means of the first actuator when starting on an incline and the parking lock can only be released via the second actuator from a certain engine power on. This makes it possible to prevent a rolling movement of the motor vehicle in an unwanted direction and to save energy and reduce wear.
The second actuator can be constructed, for example, as an electric motor or electro-hydraulically.
If the second actuator is arranged in a housing of the gearbox, a compact assembly can be achieved which can be separately manufactured and checked for its operations. However, the second actuator and, in particular, the parking lock can also be arranged advantageously outside the gearbox housing, as a result of which the gearbox can be constructed in an especially space-saving manner. The second actuator can be integrated in a wheel hub of the motor vehicle or advantageously mounted on a chassis part. As a rule, a motor vehicle chassis is connected to wheels of the motor vehicle via a spring system, as a result of which the mass of the second actuator mounted on the chassis part advantageously belongs to the spring-mounted mass.
Furthermore, a parking brake can be preferably operated by means of a second actuator which is arranged outside the gearbox housing. It is possible to use one actuator for operating the parking brake and the parking lock and, as a result, to save one actuator. In an embodiment according to the invention, it is also proposed that the parking lock and the parking brake be constructed of one piece; as a result, it is possible to save components, constructional space, installation effort and costs.
To hold the parked motor vehicle reliably without energy expenditure in the parked state, according to another embodiment of the invention, the parking lock is self-locking, such as by means of a shoe brake. So that the parking lock can also be used as a braking unit when the motor vehicle is moving at relatively large traveling speeds, however, it is advantageously self-locking only below a certain traveling speed, for example below 3 km/h.
The parking lock can also be constructed as parking lock catch.
In a further embodiment, it is proposed that, in the case of a fault in the first actuator, the gearbox can be adjusted via the second actuator at least to a limited extent; as a result, the reliability can be increased without an additional actuator.
The first actuator is advantageously arranged in a housing of the gearbox, so that it is protected against external influences such as, for example, splashed water, heat radiation from an exhaust gas system, large temperature fluctuations, etc. Furthermore, it is possible to utilize any constructional space which may still exist in the gearbox housing and to avoid additional constructional space.
As a rule, the various gearshift positions of an automatic gearbox are set via a hydraulic slide valve, by which volume flows can be appropriately controlled. The first actuator can be connected to the hydraulic slide valve via a linkage or can advantageously act directly on the hydraulic slide valve, as a result of which a rod linkage can be avoided and constructional space saved. To be able to use as many standard components as possible, the first actuator is adapted to existing gearboxes or, respectively, gearbox housings and hydraulic units.
It is also proposed that the input unit have at least one first input device, and a second input device which is independent of the first input device. In the case of a fault in the first input device, input data intended at least partially for the first input device can be input via the second input device which makes it possible to further increase the reliability.
The second input device can be formed by various devices which are known to the expert. However, an input device which, in normal operation, has a function different from that of the first input device is advantageously used, so that an additional input device can be saved. Particularly advantageously, input devices are used which, in normal operation, have no significance for the driving characteristics and can be easily omitted in emergency driving operation, such as, for example, an input device for controlling an air-conditioning system, a GPS (global positioning system), a radio cassette system, etc. When the second input device is used, the driver will be advantageously guided via a menu, for example visually via a display or aurally via loudspeakers.
The second input device can be arranged at various positions in a passenger space, preferably in the area of a steering wheel of the motor vehicle. Advantageously it can also be integrated in the steering wheel. During the input process, a driver of the motor vehicle can hold the steering wheel with both hands, so that high driving safety and high comfort can be achieved.
In a further embodiment according to the invention, input data can be entered orally into the input unit. For this purpose, existing microphones and/or existing voice recognition modules in hardware and software can be advantageously used, for example a hands-free system of a telephone, of a GPS, etc. Additional constructional space can be saved and comfort can be further enhanced.
The state of readiness to receive can be activated by means of a key and/or by means of an oral codeword; for example by activating a state of readiness to receive by means of the term xe2x80x9cgearshiftxe2x80x9d and then controlling the gearbox by means of certain terms such as, for example, xe2x80x9cforwardxe2x80x9d, xe2x80x9creversexe2x80x9d, xe2x80x9cneutralxe2x80x9d, xe2x80x9cparkxe2x80x9d, etc.
Information relating to the gearbox (for example which gear is selected, etc.) is frequently output via a display. However, it may be appropriate in various situations to output certain information audially, especially information which notifies the driver of a hazard or which was overlooked on the display over a certain period, (for example, missing park position after parking the vehicle, high revolutions of the internal combustion engine, etc.) To avoid additional loudspeakers, those which already exist are preferably used, for example of a radio cassette system, of a GPS, etc.
Comfort can be further enhanced by at least one of the controllers being connected directly and/or via a data network of the motor vehicle to a driver assistance system. It is also possible to integrate a driver assistance system in one of the two controllers.
The driver of the motor vehicle can be supported in various tasks which would be known to the expert. For this purpose, it is necessary in most cases to recognize what the driver wants.
This can be frequently achieved by detecting a number of parameters and evaluating them in association, such as, for example, traveling speed, inclination of a roadway, accelerator pedal position, position of the gearbox, rotational speed of the internal combustion engine, etc.
It is proposed that, when the motor vehicle is being parked, the actuator unit automatically closes a parking lock, and/or automatically opens the parking lock when a desire to drive off has been detected. If it is detected that the driver wishes the motor vehicle to stay at a standstill, for example by the accelerator pedal not being operated over a certain period when the motor vehicle is at a standstill, the actuator unit can advantageously automatically interrupt a flow of force between the gearbox and the internal combustion engine and, as a result, reduce the energy consumption and the wear.
Furthermore, it is proposed in an embodiment of the invention that, in the case of an impending impact of the motor vehicle against an object, the controller and/or the driver assistance system intervene(s) in the vehicle control and counteract(s) the impact, especially when the motor vehicle is being parked. It is possible to intervene in the control of the vehicle direction and especially in the control of the vehicle speed by means of the controller and/or the driver assistance system; for example, using the controller, it is possible to interrupt the flow of force between the gearbox and the internal combustion engine by means of the first actuator and to decelerate and stop the motor vehicle in front of the object by means of the second actuator via a braking unit or, respectively, by means of the parking lock. The impending impact can be advantageously detected by means of ultrasonic sensors which already exist in many motor vehicles as parking aids.
Furthermore, a movement of the motor vehicle in an unwanted direction, for example when starting on an incline, can be automatically prevented by means of the second actuator.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.